1. Field of the Invention
The present invention relates to a vertical vibrator, and more particularly, to a vertical vibrator capable of preventing vibration in a horizontal direction and reinforcing the cohesive power of a magnetic fluid.
2. Description of the Related Art
Recently, a release of personal digital assistants having large LCD screens has been rapidly increased for the convenience of users. Therefore, personal digital assistants have adopted a touch screen scheme and used a vibration motor in order to generate vibrations when the screen is touched.
The vibration motor is a part using the principle of generating electromagnetic force to convert electric energy into mechanical vibrations. The vibration motor, which is mounted in personal digital assistants, has also been used to inform a user of an incoming telephone call in silence.
The related art has used a scheme of generating a rotatory force to rotate a rotating unit having an unbalanced mass, thereby obtaining a mechanical vibration. That is, the related art has used a scheme of obtaining mechanical vibrations by performing a rectifying action on the rotatory force through a contact between a brush and a commutator.
However, the brush type structure using the commutator leads to mechanical friction, electrical sparks and foreign materials, while the brush passes through a segment of the commutator and a gap between poles of the segment when the motor rotates, thereby shortening the lifespan of the motor.
In addition, when voltage is applied to the motor, it takes time to reach targeted vibrations due to rotational inertia, such that it is difficult to rapidly implement appropriate vibrations on the touch screen.
In order to overcome the disadvantages of the lifespan and the response characteristics of the motor and implement the vibration function of the touch screen, a vertical vibrator has mainly been used.
The vertical vibrator does not generate vibrations by using the rotational principle of the motor, but generates resonance by periodically generating electromagnetic force obtained through a spring mounted in the vibration motor and a mass body hung on the spring according to a resonance frequency to generate vibrations.
In this case, the vertical vibrator mainly uses a yoke having a magnet attached to a cylindrical casing to generate vibration in a vertical direction. However, as the operation of the vertical direction becomes greater, there is a problem in that the vertical vibrator moves the mass body in the horizontal direction as well as the vertical direction.
Since the vertical vibrator uses the cylindrical casing, an elastic member provided to generate the vibrations is combined with a bending spring or a plate spring including a spaced ring, such that it is difficult to make the size of the vertical vibrator small.
Further, the magnetic fluid serving as a cushion is away from the magnet, thereby weakening adsorptive power.
Therefore, as the adsorptive power of the magnetic fluid is weakened, the force of fixing the magnetic fluid to the magnet is also weakened, such that when the vibrator is vibrated up and down, it is in direct contact with the upper structure, thereby causing touch tone and noises.